I recently got Battlefleet Gothic and have been playing my brother using the Chaos ships until the Ork ones arrive next month. We have attempted to play Secnario 8 (Escalating engagement or something) several times, but as Imperial Cruisers are slower and therefore harder to get onto the board, my brother (he's only 11) gets so frustrated at my ship all turning up and pounding the hell out of the few imperial cruisers that turn up in the first few turns, that he keeps resigning. However, I hate to give up on a battle, so I have introduced a new rule for self-destructing your ships. It runs as follows:
If you pass a leadership test you may attempt to self-destruct your ship. All you do is roll on the catastrophic damage table an amount of times equal to the amount of hit-points left on your ship.
This is very expensive in terms of ships, but is good if you're in a hopeless situation. (For example, the other day my brother had a single Tyrant-class cruiser limping across the table with a Slaughter-class cruiser and a Styx-class heavy cruiser tail-hugging it and pounding the hell out of it, and a Carnage-class sitting well out of range and pounding it from the front as well. He decided to self-destruct is as it was going to die anyway, and the fact that he managed to roll a double 6 and cripple two of my cruisers just goes to show, really.)